Mercury vapor discharge lamp with radiation plane in envelope

ABSTRACT

Improvement of a mercury-vapor lamp, characterized by the provision of a radiation plane in the form of a flat portion on the outer wall of a substantially cylindrical envelope of a mercury-vapor lamp, said flat portion being formed parallel the axis of said envelope.

United States Patent 1 1 1111 3,729,643 Hosokoshi 5] Apr. 24, 1973MERCURY VAPOR DISCHARGE LANIP [56] References Cited WITH RADIATION PLANEIN ENVELOPE I I UNITED STATES PATENTS 1751 Invent Home, Neyagaww2:233:33; 11322 22222 Z1iiiiiiiiiiiiiiiiiiiiiiii323?ii Japan 3,593,0567/1971 Degawa etal. ..3l3/l84 x [73] Assignee: Matsushita ElectronicsCorporation, Osaka Japan 2:445.o 12 7/1948 Van Orden... ..313/204 22 l M29 197 2,020,726 ll/l935 Gaidies ..3l3/2()4 PP N011 128,658 PrimaryExamineF-Palmer C. Dcmeo Attorney-Stevens, Davis, Miller & Mosher [30]Foreign Application Priority Data A T AC Ap. 3, 1970 Japan ..45/28735impro ement f a e y ap r p Characterized I v by the provision of aradiation plane in the form of a [52] F' 'i gfig flat portion on theouter wall of a substantially cylin [51 1 i J l I J drical envelope of amercury-vapor lamp, said flat por- [58] Field of Search ..3l3/l84, 220,204, on being formed parallel the axis of Said envelope 3 Claims, 4Drawing Figures Patented April 24, 1973 2 Sheets-Sheet l PRIOR ART PRIORART F/GJ Kflflfa/(mm INVENTOR ATTORNEYS MERCURY VAPOR DISCHARGE LAMPWITH RADIATION PLANE IN ENVELOPE This invention relates to improvementof a mercuryvapor lamp, characterized in that a radiation plane isprovided on a flat portion formed on the outer wall of a substantiallycylindrical envelope of a mercury-vapor lamp, parallel to the axis ofthe envelope.

Light-source devices using superhigh-pressure mercury-vapor lamps (i.e.,lamps having an internal pressure in excess of atmospheres) haveextensive applications as point sources oflight for projectors as wellas for the exposure of photosensitive films, for example, in themanufacture of phosphor screens of color picture tubes, printed circuitsubstrates, etc.

In those light-source devices, which are usually operated in combinationwith condensing lenses, the arc in the form of a columnar light-emittingpart of each light source is desired to be as small in diameter as Also,it is noted that, in such a conventional device which makes use of anare produced in the hollow of a cylindrical quartz envelope containingthe superhighpressure mercury-vapor lamp as the principal light source,the diameter of the arc column appears to be comparatively large. Thisis because the apparent inside diameter of the envelope looks largerthan the actual dimension due to the refraction of light on the outerwall of the envelope.

According to the present invention, the radiation surface is formed on aflat portion of the envelope as briefly mentioned above. Thus, whenviewed from the outside through the flat portion, the apparent insidediameter of the envelope is equal to the actual dimension. Hence, theapparent diameter of the arc column is smaller than those ofconventional columns. With such a construction, the mercury-vapor lampin accordance with the present invention exhibits far better luminancedistribution characteristics than those of prior art lamps.

The invention will be better understood from the following descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevation view, partly broken away, of a light-sourcedevice using a conventional superhighpressure mercury-vapor lamp;

FIG. 2 is a section view taken on the line IIII of FIG. 1;

FIG. 3 is a section view of a superhigh-pressure mercury-vapor lampembodying the present invention;

FIG. 4 is a graph comparing the luminance distribution characteristicsof a lamp according to the invention and a conventional lamp.

A conventional light-source device of the nature described, as can beseen from FIG. 1 and also from FIG. 2 which shows a section along theline II-II of FIG. 1, is constructed with a base I having sockets, asuperhigh-pressure mercury-vapor lamp 2 supported by the base 1generally parallel to the axis of the base, and a sealed envelope 3 ofquartz for the lamp. The envelope 3 is formed with a cylindrical portion4 having an inside diameter d), and an outside diameter (b so that anarc column produced in the center hollow serves as a principal lightsource. The apparent inside diameter 4 of the envelope 3 as viewed fromeither of the directlons indicated by arrows in FIG. 2 is larger thanthe actual inside diameter because of refraction of the light throughthe outer wall surface of the envelope 3. Accordingly the diameter ofthe arc column looks relatively large.

By contrast, a mercury-vapor lamp according to this invention, as shownin FIG. 3, has a quartz envelope 13 which is formed with a flat portion14 parallel to the axis P of the envelope 13 on the outer peripheralwall surface. This flat portion 14 constitutes a radiation plane. Itswidth W is larger than the inside diameter d), and extends across thesame. The flat portion 14 is formed by cutting and grinding or otherwisemachining the envelope of an ordinary superhigh-pressure mercury-vaporlamp. Alternatively, it may be formed simultaneously with the envelope13.

With the superhigh-pressure mercury-vapor lamp above described, theapparent inside diameter 4V which is viewed through the flat portion 14,is equal to the inside diameter Q5 Therefore, the apparent diameter ofthe arc column that is formed inside the envelope 13 is smaller thanthose of conventional superhighpressure mercury-vapor lamps. In thefigures, reference letter a indicates an arc, and reference letter Drepresents the extent of the flat portion.

In the light-source device of this invention, the superhigh-pressuremercury-vapor lamp is mounted on the base in such a manner that the flatportion 14 serves as a radiation plane. Its luminance distributioncharacteristic in percentage is compared in FIG. 4 with that of aconventional device. From the figure it can be seen that the former,represented by a curve A, is by far superior in centralizability to thelatter represented by a curve B. The center axis of ordinate Crepresents a straight line normal to the axis P of the envelope andwhich passes through the center of the envelope. On the axis of abscissais plotted the radial distance from the envelope.

What is claimed is:

1. In a mercury-vapor discharge lamp including a light-transparentelongate envelope with an electrode sealed at each end, the improvementwherein said envelope comprises a completely cylindrical inner wallcoaxial with the longitudinal axis of said envelope and an outer wall,said outer wall having a cylindrical portion coaxial with saidlongitudinal axis and a flat portion parallel to said axis, the radialthickness of said envelope at said flat portion being less than at saidcylindrical portion, said flat portion serving as a radiation plane.

2. A mercury-vapor lamp according to claim 1 in which said lamp is ofthe superhigh-pressure type.

3. A mercury-vapor lamp as defined by claim 1 wherein the width oftheflat portion of the outer wall of said envelope is greater than thediameter of the inner cylindrical wall of said envelope and extendsthereacross.

1. In a mercury-vapor discharge lamp including a lighttransparentelongate envelope with an electrode sealed at each end, the improvementwherein said envelope comprises a completely cylindrical inner wallcoaxial with the longitudinal axis of said envelope and an outer wall,said outer wall having a cylindrical portion coaxial with saidlongitudinal axis and a flat portion parallel to said axis, the radialthickness of said envelope at said flat portion being less than at saidcylindrical portion, said flat portion serving as a radiation plane. 2.A mercury-vapor lamp according to claim 1 in which said lamp is of thesuperhigh-pressure type.
 3. A mercury-vapor lamp as defined by claim 1wherein the width of the flat portion of the outer wall of said envelopeis greater than the diameter of the inner cylindrical wall of saidenvelope and extends thereacross.